1. Field
The present disclosure relates to cameras. In particular, exemplary embodiments relate to cameras for measuring a depth image and methods of measuring a depth image using the same.
2. Description of the Related Art
A depth image of an object may be measured by the following two methods. In a first method, a depth image is obtained by using a pattern light and an optical trigonometry like Kinect. In a second method, after irradiating an infrared IR ray toward an object, a depth image is extracted based on a time-of-flight (TOF), that is, the time required for the IR ray to return to a camera after the IR ray is reflected by the object.
A TOF camera creates a depth image such that, after irradiating a non-visible light, that is, a near IR ray having a wavelength of 850 nm, to an object after modulating the non-visible light to a few tens of MHz, a phase delay of the light that returns to the camera from the object is measured by using an image sensor, and a distance between the object and the camera is obtained from each pixel of the image sensor. Thus, the depth image is created from the distances obtained from the image sensor.
A common feature of depth cameras is that a depth image is taken using a self-illumination. A related art depth camera using TOF has been developed using an LED as a direct illumination without an additional optical system, or has been developed with an illumination which is uniformly irradiated in a field of view.
A depth camera using TOF (hereinafter, a TOF camera) mainly measures a depth image using a homodyne mixing method. In this method, a distance is calculated using an intensity of light that is received in each pixel of an image sensor. Therefore, the illumination should be uniformly irradiated to a space in a field of view of the TOP camera. When the illumination is not uniformly irradiated to space in the field of view, a depth image cannot be obtained for a location where the illumination does not reach. Thus, a resolution of the depth image is reduced.